The primary objective of this research proposal will be to determine the physiological significance of H3-cortisol and H3-dexamethasone binding to bovine mammary tissue. Mammary tissue slices will be incubated with tritiated corticoids with and without unlabelled corticoids, and the distribution of radioactivity among the epithelial, fibroblast and adipose cells of bovine mammary tissue from calves, pregnant heifers and lactating cows will be determined from autoradiograms. I expect that mammary secretory epithelial cells will be the predominant cells which bind corticoids. Other studies will focus on the ability of mammary tissue to bind H3-dexamethasone infused locally through the pudic artery where it enters the mammary gland. We will also determine if the H3-dexamethasone is transferred into milk. Serum cortisol in the mammary (pudic) artery and mammary vein will be measured in cows in various physiological states. We expect to find the greatest amount of cortisol taken up from the arterial blood by the mammary gland of lactating cows. Attempts will be made to saturate the corticoid binding sites of the mammary tissue with exogenous administration of unlabelled corticoids. We plan to determine the hormonal requirements for maintenance of maximal uptake of C14-glucose and alpha-lactalbumin synthesis in mammary explants from lactating cows. We will subsequently relate corticoid binding activity in the explants with the uptake of C14-glucose and alpha-lactalbumin.